Ryan Grant went over for Glasgow's only try

Once again a lack of composure and individual errors cost Glasgow dear as they went down to their third home loss in a row.

The visitors started the brighter, buoyed by their 29-20 victory in the reverse fixture at Cardiff Arms Park a week ago, and it didn't take long for Rhys Patchell to turn their possession into points as the youngster used the significant breeze to his advantage and kicked a mammoth penalty from well inside his own half.

Leigh Halfpenny took over the kicking duties from closer range to double the lead midway through the first half.

Glasgow began to dominate at scrum time and were camped on the Cardiff line for ten minutes with Sam Hobbs sent to sinbin.

The Warriors looked like they had opened their account when Nikola Matawalu dived through to touch down, but the score was ruled out when the TMO decided Rob Harley had impeded a Cardiff player - a marginal call. Cardiff held on to go into the break 6-0 ahead.

The opening period was littered with errors and stoppages and things didn't exactly improve after the restart but the Blues didn't care when Halfpenny extended the advantage even further with another excellently judged penalty from out wide.

The home side finally got on the scoreboard with 10 minutes left as replacement scrum-half Chris Cusiter delivered a fine inside ball to prop Ryan Grant, who powered his way over from short range. Duncan Weir swiftly added the conversion.

There was only one team in it for the remainder of the match as the Warriors hammered on the door but substitute Weir missed an opportunity to snatch victory with three points from the tee and the Blues' defence held firm.

The vital away win takes the Welshmen to the top of Pool Two, at least temporarily, and keeps them well in the hunt for qualification when the competition resumes in January but Glasgow are now left to concentrate on the league.

Glasgow coach Gregor Townsend felt his side should have been awarded a penalty try when Cardiff skipper Sam Hobbs was sin-binned by French referee Pascal Gauzere for the third scrum offence in quick succession.

His frustration was soon compounded when Robert Harley was penalised for obstruction by the video referee after Nikola Matawalu had dived over in the 36th minute.

Gregor said: "I have to say the try that Niko scored was a clear try in my book. If you're clearing a ruck and someone hits and goes through that hole, then it's a try. I must be coaching something different, I don't know those laws.

"And to have penalty after penalty from scrum and from them to kick through the ball at the scrum, illegally I believe, and not to get a penalty try for that was very frustrating and disappointing.

"The effort to put into that and score what we believe were two tries and get nothing was tough."